What Are Differences Between Single-Phase and Three-Phase Energy Meter?

In contexts related to supply of electricity, especially if you have been informed about how your contract with the electricity company works, you may have heard of single-phase or three-phase meter. What to know, in brief:

  • Single-Phase energy meter is generally used in ordinary homes and is sufficient for energy needs of standard household appliances and systems.
  • Three-Phase energy meter is more common in industrial settings or for homes with higher consumption.
  • Installing three-phase and single-phase meter has same cost. What changes is cost of power quota, which depends on power contracted for home.

What is Three-Phase Energy Meter and When is it Used?

Before understanding what to choose between three-phase and single-phase meter, let’s try to understand what is meant by these terms.

When we talk about three-phase energy meter, we are referring to device used to measure consumption of electrical energy in three-phase system, mode of energy distribution characterised by the presence of three distinct electrical phases.

Three-phase system is widely used in energy production and distribution for its efficiency: it allows same amount of energy to be transported using less material and reducing power losses along transmission lines. 

Three-phase meter is indicated when electrical loads are high, in particular:

In these contexts, in fact, using single-phase system could create imbalances in electrical network, with potential technical problems such as voltage drops. However, if the required power is limited, for example 1.5kW, the use of three-phase meter is not very advantageous.

Keep in mind, then, that it is local distributor who decides whether or not to accept installation of three-phase meter or its conversion based on an assessment of compatibility with network to avoid imbalances.

How Three-Phase Current System Works

Three-Phase system consists of three phase wires and neutral wire, which together allow for distribution of electrical energy in balanced manner.

Three phase wires carry alternating currents that oscillate sinusoidally, but with phase shift of 120° between them, meaning that each phase reaches its maximum peak at different times. 

It is precisely this mechanism that ensures constant and uniform flow of energy which also allows for reduction in losses and improved efficiency compared to single-phase systems. 

As we have already mentioned, this system is mainly used in areas that require greater power, such as industries, large buildings or complex plants.

When to Install Three-Phase Kilowatt Meter

Installation of three-phase meter may be necessary in some situations, especially:

  • In industrial sector for high power (15kW, 20kW or more): it is essential in industries, artisan workshops or workshops that use high-power machinery. Power of this magnitude cannot be managed with single-phase meter, which would be inadequate to support required energy loads;
  • In households with high electricity consumption: some homes with complex systems or large appliances may require three-phase meter. For example, homes with heat pumps , professional kitchens or swimming pools consume lot of energy and benefit from three-phase system to better distribute the load (in these cases, consumption exceeds the typical capacity of single-phase system, generally around 3 kW). 

Single Phase Kilowatt Meter: What It Is and When to Use It

Now that we understand how three-phase current system works, let’s try to understand mechanism behind single-phase system and when installing single-phase meter is most suitable.

Single-Phase meter is device that measures consumption of electricity in systems powered by system with only two cables: one phase and one neutral.

This is most common type of electricity meter in homes and common households, where electricity is mainly used for lighting and standard household appliances such as refrigerators, washing machines, dishwashers and televisions. 

In fact, this system is particularly suitable for users with medium-low contractual power, typically equal to 3kW , but can be adjusted with powers between 1.5kW and 6kW, depending on the needs.

In particular cases, single-phase supply can reach higher powers, up to 10kW , but this occurs rarely and only if continuous or high loads are not required that would justify three-phase meter.

What is Difference Between Three-Phase and Single-Phase Energy Meter?

From what has just been said, the difference between three-phase and single-phase meters will now be clearer to you. We can summarize the main characteristics and differences in this table:

CHARACTERISTICSINGLE-PHASE METERTHREE-PHASE METER
Voltage230V380V between two phases, 230V between one phase and neutral
Intended useDomestic usersIndustrial or domestic environment with high consumption
Number of cables2 (1 Phase + Neutral)4 (3 Phases + Neutral)
PowerFrom 1.5kW to 6kW (up to 10kW in exceptional cases)Over 6kW, typically for high power
ApplicationsLighting, small and medium appliancesIndustrial machinery, heat pumps, complex systems

How much does it cost to switch from single-phase to three-phase?

When you need to activate an electricity supply, you can choose whether to install a single-phase or three-phase meter. A decision that, as we have seen, depends mainly on your needs.

You will, in fact, have to consider intended use: If system will be used for lighting and standard household appliances, single-phase meter will certainly be sufficient. On the contrary, if you plan to power powerful machinery, a three-phase meter may be more suitable. 

Furthermore, you will have to evaluate contractual power: for requests greater than 6 kW, three-phase system is often the only choice to guarantee stability and prevent problems of imbalance on network.

Another factor you will have to consider is costs. Be careful, because the cost of connecting meter does not vary based on whether it is single-phase or three-phase, but rather depends on power required.

This is because the cost is related to amount of energy that the system must be able to handle, not to type of meter installed.

It must be said, however, that three-phase system with high power will lead to higher recurring costs linked to “power quota” present in bill, so choice must be made carefully to avoid unnecessary expenses. 

Switching From Three-Phase to Single-Phase Meter

What if after moving to new home you discover that previous owner has installed three-phase meter that you don’t need? In these cases, advice is to keep it, without making the switch from three-phase to single-phase. As we have seen, in fact, with the same contractual power, costs on bill do not change. 

Changing meter would entail an additional cost for replacement that may be unnecessary if power required is adequate for existing system. Therefore, if the three-phase meter meets your needs, it is not necessary to replace it just to change to single-phase.